Story highlights

It would require police to check to immigration status if there is "reasonable suspicion"

The justices could use the appeal to address broad constitutional questions

Arizona is the nation's most heavily traveled corridor for illegal immigration

The Supreme Court is poised to decide whether Arizona can enforce its controversial immigration law over the strong objections of the Obama administration. Oral arguments will be held Wednesday.

A ruling during a presidential election year could generate renewed political attention on an issue that has been building in intensity in recent years.

Federal courts have blocked four key parts of the state's Support Our Law Enforcement and Safe Neighborhoods Act, known as SB 1070. Arizona has argued that illegal immigration is creating financial hardships and safety concerns for its residents, and that the federal government has long failed to control the problem.

The administration has countered by saying immigration issues are under its exclusive authority and state "interference" would only make matters worse.

The southwest state is the nation's most heavily traveled corridor for illegal immigration and smuggling.

Justice Elena Kagan will not hear this case, because as solicitor general, before taking the bench last year, she had been involved in the administration's initial legal opposition to the law. A 4-4 high court split would be likely to keep the Arizona law in legal limbo, preventing the four provisions of the law from going into effect, but not settling the larger constitutional questions.

It would also shift the election-year fight over the issue to other states with current or pending crackdown laws.

The four Arizona provisions currently on hold are:

-- A requirement that local police officers check a person's immigration status while enforcing other laws, if "reasonable suspicion" exists that the person is in the United States illegally.

-- A provision authorizing police to arrest immigrants without warrant where "probable cause" exists that they committed any public offense making them removable from the country.

-- A section making it a state crime for "unauthorized immigrants" to fail to carry registration papers and other government identification.

-- A ban on those not authorized for employment in the United States to apply, solicit or perform work. That would include immigrants standing in a parking lot who "gesture or nod" their willingness to be employed.

Although the specific question before the high court relates to the law's enforcement, the justices could use the appeal to address the broader constitutional questions. Similar laws are under challenge in lower courts in Georgia, Alabama, Utah and South Carolina. Arizona's appeal is the first to reach the Supreme Court.

Arizona Gov. Jan Brewer said she is confident the high court will rule for the state.

"This case is not just about Arizona. It's about every state grappling with the costs of illegal immigration. And it's about the fundamental principle of federalism, under which these states have a right to defend their people," the Republican governor said in a statement released after the Supreme Court agreed to decide the matter.

"Arizona has been more than patient waiting for Washington to secure the border. Decades of federal inaction and misguided policy have created a dangerous and unacceptable situation and states deserve clarity from the court in terms of what role they have in fighting illegal immigration."

At issue is whether states have any authority to step in to enforce immigration matters or whether that is the exclusive role of the federal government. In dry legal terms, this constitutional question is known as "pre-emption."

Arizona officials will tell the justices they are merely assisting and cooperating with federal authorities, action they say Congress has blessed.

But the administration -- backed by a variety of immigrant and civil rights groups -- says allowing such state authority would hurt relations between the United States and other countries, disrupt existing cooperative efforts and unfairly target legal immigrants.

In a rhetorical rematch of last month's separate arguments over the Obama-backed health care reform law, private attorney Paul Clement will make the case for Arizona while Solicitor General Donald Verrilli will articulate the federal government's position.

The legislation has a variety of supporters and detractors.

Republican lawmakers, outspoken Maricopa County, Arizona, Sheriff Joe Arpaio, and various state governments were among those filing briefs supporting the law. The Mexican government, the Anti-Defamation League, the American Immigration Lawyers Association and the city of Tucson, Arizona, were among those supporting the Justice Department's side.

In its petition to the high court, Arizona says it is the nation's busiest illegal entry point, with many people streaming in from neighboring Mexico.

"Arizona bears the brunt of the problems caused by illegal immigration. It is the gateway for nearly half of the nation's illegal border crossings," said state officials. "Beyond the obvious safety issues, the fiscal burdens imposed by the disproportionate impact of illegal immigration on Arizona are daunting. Arizona spends several hundred million dollars each year incarcerating criminal aliens and providing education and health care to aliens who entered and reside in the country in violation of federal law."

Civil rights and minority groups-- as well as some law enforcement agencies-- worry the law would only encourage racial profiling, drain vital and scarce law enforcement resources, hamper investigation of more serious crimes, and cripple relations with immigrant communities.

In a CNN/ORC International poll last fall, 52% of those surveyed said illegal immigration was extremely or very important to their vote for president. But a similar poll in March showed only 4% saying it is the most important issue facing the United States today, while 53% said the economy is the top issue.

While a federal judge in 2010 stopped enforcement of the most controversial provisions, other parts of SB 1070 were given the go-ahead, including a ban on "sanctuary cities," or municipalities with laws or policies that render them relatively safe for undocumented immigrants.

Judge Susan Bolton's ruling also allowed a provision making it illegal to hire day laborers if doing so impedes traffic. And her order allowed parts of the law dealing with sanctions for employers who hire illegal immigrants to take effect.

A federal appeals court in San Francisco subsequently sided with the Justice Department, largely on the argument that federal immigration policy -- as well as America's standing in the world -- would be greatly undermined if individual states adopted their own separate immigration laws. Doing so, the court concluded, essentially meant a given state would be adopting its own foreign policy, one that may be in opposition to national policy.

"That 50 individual states or one individual state should have a foreign policy is absurdity too gross to be entertained. In matters affecting the intercourse of the federal nation with other nations, the federal nation must speak with one voice," Circuit Judge John Noonan wrote in a concurring opinion.

The Arizona appeal could set important precedent on similar laws pending across the country.

In the first half of 2011, state legislatures in all 50 states and Puerto Rico have introduced a record number of bills or resolutions relating to immigrants or refugees, according to a report by the National Conference of State Legislatures. Through June, states had introduced 1,592 such bills or resolutions, compared to 300 in 2005.

The case is Arizona v. U.S. (11-182) and is to be the last argued before the high court this term. A ruling could come in late June, just before the justices recess for the summer.